It's an indication of the pressure his Government has had to absorb over the past 12 months.

A torrid 2012 ended with National on the back foot over its failure to respond to a slow-burning housing crisis, the ongoing Novopay debacle and a lack of urgency on jobs.

By launching 2013 in such dramatic fashion, Mr Key has signalled his intention to draw a line under those failures and regain the political initiative.

Right-hand man Steven Joyce has been parachuted in to fix up the Novopay mess. Mr Heatley has been dumped for a rehabilitated Nick Smith, whose elevation to the housing portfolio is a response to National being caught flat-footed by Labour on the issue.

Mr Key's state-of-the-nation speech on Friday will flesh out the Government's response to the third issue on which National is most vulnerable - jobs.

Ms Wilkinson and Mr Heatley might feel hard done by. Trouble-prone Education Minister Hekia Parata's survival will only rub salt in their wounds. But Ms Parata has had only a year in the job. Mr Key is prepared to give her more time.

After four years, Mr Heatley's and Ms Wilkinson's time has run out. They make way for new talent, including Nikki Kaye, whose elevation to Cabinet will bolster her prospects of holding on to Auckland Central.

Mr Key made no bones yesterday about the reason for his sense of urgency to bring fresh blood into Cabinet - he did not want to repeat the mistakes of his cautious predecessor Helen Clark, who failed to rejuvenate her lineup.

He has also thrown down the gauntlet to Labour leader David Shearer, who will unveil his own reshuffle in coming weeks.

But the stakes are high. Any other prime minister might have balked at exposing themself to the prospect of not one but two by-elections, should either of the MPs he humiliated spit the dummy.

Ms Wilkinson's Waimakariri seat could easily swing back to Labour, putting National's majority on a knife edge. But he has gambled on that not happening.